Troubleshooting Flow Chart For Synthesizer - Motorola GM328 Service Manual

3-6
3.0

Troubleshooting Flow Chart for Synthesizer

Check D4201,
C4202, C4203, &
C4206
YES
NO
5V
U4201 Pin 47
at pin 6 of
at = 13VDC
D4201
NO
Check
R4201
Is
U4301 Pin 19
<40 mVDC in RX &
>4.5 VDC in TX?
(at VCO section)
?
YES
Is
RF level at
U4201 Pin 32
-12 < x <-25
dBm
?
YES
Are
R4221,R4222,
R4223,C4221,
C4222,& C4223
OK?
YES
Replace
U4201
NO
Correct
Problem
Is
?
YES
Check C4381
NO
Is
U4201
YES
Pin 2 >4.5 VDC in
Tx & <40 mVDC
in Rx
?
NO
Replace
U4201
If L4225, C4229 & C4227
NO
are OK, then see VCO
troubleshooting chart
Replace or
NO
resolder
necessary
components
Start
Visual
check of the
Board
OK?
YES
+5V
at U4201
NO
YES
Pins
13 & 30
?
Check 5V
R e g u l a t o r
U4211
Are
signals NO
at Pins 14 &15
of U4201
?
YES
Is
there a short
NO
between Pin 47 and
Pins 14 & 15 of
U4201
?
YES
Remove
Shorts
Troubleshooting Flow Chart for Synthesizer
5V
NO
Check 5V
at U4201
Regulator
pins 5, 20, 34
U4211
& 36
YES
Is
Is
16.8MHz
16.8MHz NO
signal at
Signal at U4201
U4201 Pin
Pin 19
23?
?
YES
Check
Y4261 / Y4262 and
associated parts
Are
Waveforms
NO
at Pins 14 & 15
triangular
?
YES
NO
of U4201 toggle
when channel is
Check programming
lines between
U0101 and U4201
Pins 7,8 & 9
NO
from µP U0101
Check µP U0101
Troubleshooting
Chart
Replace
U4201
YES
NO
Do
Pins 7,8 & 9
changed?
YES
Is
information
correct
?
YES
Replace
U4201